Combustion of fast pyrolysis bio-oil and blends in a micro gas turbine

Abstract

The use of Fast Pyrolysis Bio-Oil (FPBO) as fuel was studied in a small scale non-regenerated micro gas turbine, set up in a dedicated test rig. The system includes a dedicated injection line and a modified combustor to burn efficiently high volume fractions of FPBO-in-ethanol solution. The effect of the larger combustor volume improved the quality of the combustion of the reference diesel oil and pure ethanol as regards exhaust emissions, while maintaining unchanged fuel consumptions of the original configuration. Tests with 20/80 and 50/50% (volume fractions) of FPBO/ethanol blends showed successfully and stable engine operation. By increasing the FPBO volume fraction in the fuel blend, an increase in CO emissions was observed - probably due to the larger droplets derived from the more viscous fuel - as well as in NOX emissions - probably due to fuel-bound nitrogen. Considering the proposed modifications and FPBO/ethanol blend as fuel, the engine reached an overall electrical efficiency higher than that measured with benchmark diesel fuel. A final run with 100% FPBO feeding showed unstable combustion with the presence of carbon deposits in the hot parts of the system, showing that the present configuration requires further modifications to achieve this goal. Guidelines were provided for the implementation of further upgraded solutions for MGTs towards viscous, acidic and aqueous fuels feeding.